Suspended roof construction



Jan. 13, 1970 F. oTTo ET AL 3,489,156

SUSPENDED ROOF CONSTRUCTION Filed Feb. '7, 1966 2 Sheets-Sheet l //V VENTORS Fre/ Offo Pefer Sfrom eyer Jan. 13, 1970 F. o'r'ro ET AL 3,489,156

SUSPENDED ROOF CONSTRUCTION Filed Feb. 7, 1966 2 Sheets-Sheet 2 Fl g Y W M fifforggys United States Patent 3,489,156 SUSPENDED ROOF CONSTRUCTION Frei Otto, Berlin-Zehlendorf, and Peter Stromeyer, Litzelstetten, Germany, assignors to L. Stromeyer & C0., G.m.b.H., Konstanz, Germany Filed Feb. 7, 1966, Ser. No. 525,659 Claims priority, application Germany, Feb. 5, 1965, St 23,319 Int. Cl. A45f 1/10 US. Cl. 135-1 1 Claim ABSTRACT OF THE DISCLOSURE A suspended roof construction having a sheet-like member and holding means to tension such member. A loop of flexible material which may be a tow rope connects the holding means to the sheet-like member. The loop is secured to and lies entirely in the plane of the sheet-like member. The connection between the holding member and the loop will allow the tension forces to which the loop is subjected to pass practically through one point and under such conditions the loop assumes the shape of a continuous curve.

The present invention relates to a suspended roof construction having a sheet-like member and at least one holding member serving to tension the sheet-like member.

The invention relates therefore to roof structures, employing tenting, pre-stressed steel nets and rope netting, particularly the form of supported rope netting employed for suspended roofs, which are tensioned according to the curved membrane principle, particularly in the case of the smallest surface units, in saddle-shaped curvature, and in which this tension is efiected by supporting masts or towropes, which act thereon more or less normally to the surface of the structure within its extent and not at its outer edges.

The simple supporing mast and similarly the towrope are however, by their nature, only capable of imparting or receiving a localised force if they act directly on the surface in the said way. Therefore, as is known, a fitting with a suitable intermediate member is required at every point of attachment, so that from the localised force a distributed load results in the sheet-like surface of the structure, and indeed an adequately uniformly distributed load, and so that the resultant tension in the sheet-like member increases gradually and without a pronounced peak above the pattern of tension in the remaining regions of the surface which are not so near to the point of attachment. The tension in the sheet-like member should thus reach, in the neighborhood of the supporting mast or towrope where it has a maximum value, a value which is only a moderate amount above the average value of the tension in the sheet-like member. How well or badly this rule is fulfilled will in each case depend, as is known, on the nature of the roof construction or the shape of the structure. Accordingly it is considered that the surface of the sheet-like member should not be stretched either to a pronounced peak or to a vary steep bulge outwards or inwards by the force of the supporting mast or towrope.

In order to arrive at an adequately high mean value of tension in the sheet-like member (without excessive maximum values) with the minimum number of supporting masts or towropes, it has been customary hitherto to provide each supporting mast with a large softly rounded supporting head somewhat in the shape of a mushroom (see Deutsche Bauzeitung, 65th year (1960),

page 358 and Figure d) or in a feathered form as a socalled rounded wood feather (see ibid. page 361 and Figure 31). For the towrope however it has already been proposed to interpose between the towrope and the sheet-like member an intermediate member adapted to bear the load and shaped into the form of a funnel, i.e. with the smallest diameter of this intermediate member at the towrope and the largest diameter at the surface of the sheet-like member.

We have now found that the relatively high cost and weight and the disadvantageous additional strain on the masts, particularly during erection of the masts due to the unwieldly suporting head and its weight, of the known arrangements, and not least the architectural defects which the intermediate member constructions hitherto known clearly show, can all be avoided by a construction according to the invention.

We have found that a rope laid in a sufiiciently wide loop and secured in this extended form to the surface of the sheet-like member serves as a highly desirable intermediate member for a suspended roof construction.

In accordance with'this concept, which relates to the simplest embodiment of the invention, the above mentioned rope may be laid as a wide loop on or in the surface of the sheet-like member and firmly secured to the material of the same along the whole or almost the whole of the circumference of the loop, for example continuously sewn on or in, if the sheet-like member consists of tent cloth; and the supporting mast or the towrope is attached at a single point of the circumference of the loop so that there results between this and the loop what in building terms is known as a point" power connection. The function of the arrangement according to this invention may however just as well be explained as follows: All the tension forces in the sheet-like member around the attached loop are concentrated by means of the same to a single point, i.e. the point of attachment of the supporting mast or towrope, so that, resulting from these forces, a single force is to be imagined at the said point, namely the counterforce necessary to oppose the single stretching force applied by the supporting mast or towrope.

The roof construction forming the subject of the present invention is accordingly characterised by the fact that the sheet-like member is connected with the holding member by at least one loop which is secured to the sheet-like member in such a way that it absorbs the tension forces in the sheet-like member acting thereon and transmits them to the holding member.

The tension forces in the sheet-like member naturally increase in the direction towards the loop up to the region of attachment of the loop; the increase is, however, not continued into the region enclosed by the loop. This inner region-and this represents an important feature of the inventionmay be made weaker, more elastic, or of another material than the rest of the sheet-like member, said other material being such that sufficient flexibility of the whole is ensured at the attached loop.

Instead of specially constructing the region enclosed by the loop or leaving it like the rest of the sheet-like member, this region may even, if desired, be wholly removed, and this is also within the scope of the invention.

The opening formed by the removal of the region within the loop may then be covered by any construction, for example with a skylight, but preferably in such a way that this construction does not exert undue influence on the tension forces in the sheet-like member. The opening formed may however also be used as a passage, for example as a passage for the top of a supporting mast, for ropes and for other possible structural elements and parts 3 of apparatus. A cover or closure means may also be provided.

In a preferred arrangement according to the invention, the loop adopts a characteristic curved form which tends towards a solid curve of uniform curvature, although in practice, such an ideal curve is not always achieved owing to the inhomogeneities always present in the sheet-like material.

In a further embodiment of the invention, the converging tension forces in the sheet-like member may be transmitted, to a point support, in practice the relatively small cross-section or circumference of a supporting mast or towrope, through a plurality of loops forming a group. These individual loops of the group may be the same as each other as far as their diameter is concerned. The individual loops are preferably disposed symmetrically with respect to each other and arranged so that the axis of the supporting mast or towrope coincides with or is located close to the centre of this symmetry. Alternatively, the loops of the group may have different diameters and thus enclose surface regions of different areas. On one and the same sheet-like member, a plurality of spaced-apart loops and/or a plurality of spaced-apart groups of loops may be attached, and if desired, supporting masts and/or towropes therefor may be employed and spaced apart in the same way.

In addition to sheet-like members of, for example, tent cloth or sheet metal, the principle of roof construction according to the invention may also be realised, as already mentioned, with a stretched rope netting, and in particular with a rope netting which is braced or may be covered or lined with roof skin material of a great variety of types including rigid types. In the case of a sheet-like member of netting, the loop or the group of loops may be secured directly to the meshes of the rope netting over the whole or substantially the whole circumference of the loop. The netting may have square, rectangular, triangular or possibly even a rhombic mesh formation, prior to its being stretched in a curve.

The regions enclosed by the loops may also be removed in the case of a sheet-like member of netting. In this case, each strand of the net should be firmly and carefully tied off at its cut end, mesh for mesh, at the loop, so that the removal of the enclosed region does not cause tearing of the netting. In general it is therefore better in the case of rope netting to abstain from cutting out the regions en closed by the loops. Naturally however, the connection between the loop and the netting should be carried out as far as possible at every netting mesh touched by the loop and at all sides of the same. In every case, therefore, provision should be made for a reliable and positive fixing of the loop to the netting of adequate strength in all directions.

Three particularly simple embodiments of the invention will now be described, by way of example, with reference to the accompanying schematic drawings, in which:

FIGURE 1 is a perspective view of a first embodiment of structural surface which is tensioned to a curved membrane by a single towrope;

FIGURE 2 is a side elevation of the structural surface of FIGURE 1 viewed in the direction of the arrow A in FIGURE 4;

FIGURE 3 is a side elevation of the same structural surface viewed in the direction of the arrow B in FIG- URE 1;

FIGURE 4 is a plan from above of the same structural surface viewed in the direction of the arrow C in FIG- URE 1;

FIGURE 5 is a perspective view of a second embodiment in which a supporting mast is used instead of a towrope, and

FIGURE 6 is a perspective view of a further embodiment of the arrangement shown in FIG. 5.

In the embodiment shown in FIGURES 1 to 4, 1 denotes a sheet-like member which may be for example a membrane for covering a certain area (e.g. a building site). This membrane is stretched at its four corners on the tips of pylon-like posts which are shown purely symbolically. A towrope 2 is anchored at one end 3 in the building site; the other end of the towrope is connected to a looped rope 4 which, starting from the latter end of the towrope, forms a closed loop. The looped rope 4 is secured, for example sewn, along its entire length to the under surface of the membrane 1.

The surface of the membrane 1 bounded by the looped rope 4 is cut out in the present embodiment so that an opening is formed at the place indicated with the reference numeral 5. As a result of the downward traction of the towrope 2, the looped rope 4 is curved downwardly and in consequence imparts a curved surface to the membrane 1 attached thereto.

Stretching of the membrane 1 at its edges may be effected in any way and is not critical as regards the present invention.

A modified embodiment is shown in FIGURE 5. Whereas the holding member serving to tension the membrane is a towrope in the embodiment shown in FIGURES l to 4, in FIGURE 5 a supporting mast 8 is used which rests on the building site (for simplicity, only a portion of the mast 8 has been shown in FIGURE 5). The mast 8 projects through an opening 10 provided in a membrane 9. A collar 11 is secured to the portion of the mast 8 lying above the membrane 9, the collar 11 carrying a laterally projecting arm 12. This arm 12 serves to anchor the free end of a rope loop 13 surrounding the opening 10 and secured to the membrane 9. The traction required to tension the membrane 9 is transmitted from the mast 8, via an extension 13 to the loop 13 and thus to the membrane 9 so that the membrane acquires an upwardly curved surface.

The manner in which the end of the loop 13 is secured to the mast 8 is capable of wide modification. In FIGURE 5, the arm 12 is provided with a radial slot opening outwardly in which the extension 13 is located and then locked in position by known means.

In the embodiment shown in FIGURE 5, in transmitting the traction from the mast 8 to the loop 13, an undesirable moment is generated which applies bending stress to the mast 8. To equalise this moment a plurality of loops 14a, 14b (FIGURE 6) may be arranged symmetrically on a circle concentric with the axis of the mast. The mast 8 in this case projects through an opening made for it in the membrane 9'.

The above mentioned undesirable bending moment may however also be avoided by providing the loop 13 (FIG- URE 5) not only with the extension 13 but also with a second extension (not shown) which should, with respect to the mast 8, be diametrically opposite to the extension 13 but in other respects may be constructed and secured to the loop 13 in just the same way as the extension 13 The above described embodiments are merely examples serving to illustratae the invention and which may clearly be modified in many ways by an expert, within the scope of the ensuing claims.

The construction forming the object of the present invention has been illustrated by way of two embodiments, where the sheet-like member extends in a substantially horizontal plane. The above described tensioning means may, however, be also used in connection with sheet-like members extending in a substantially inclined or vertical plane with respect to the surface of the site. It is, therefore, explicitly mentioned, that the term roof construction used in the specification and claims is to be understood quite independently from the general position of the corresponding sheet-like member, i.e. the membrane, the rope netting etc.

What we claim is:

1. A suspended roof construction having a sheet-like member and at least one holding member in the form of 5 a mast serving to tension said sheet-like member, said sheet-like member having an opening for the throughpassage of said mast, at least two loops of flexible material are arranged symmetrically on said sheet-like member on a circle generally concentric With said opening and con- 5 necting said sheet-like member to said mast, at least one of said loops being secured to and lying substantially entirely in the plane of said sheet-like member, the free end of each loop being anchored to that part of said mast projecting above said sheet-like member, the connection between said holding member mast and said loops allowing the tension forces gathered by said loops to pass practically through one point, and said loops under the influence of these forces each assuming the shape of a continuous curve.

6 References Cited UNITED STATES PATENTS 858,875 7/1907 Knabenshue 1351 1,081,699 12/1913 Richling 135-1 1,410,820 3/1922 McMillan 1351 X 1,730,565 10/1929 Flintjer 1351 X FOREIGN PATENTS 872,395 3/1953 Germany.

10 131,872 10/1920 Great Britain.

PETER M. CAUN, Primary Examiner US. 01. X.R. 15 135-5, s 

